1. Field of the Invention
The present invention relates generally to a parallelism stabilization structure of dual-shaft hinge, and more particularly to a dual-shaft hinge mounted on a pivotally openable/closable electronic apparatus. The present invention also relates to a fixing unit, which helps in fixing the parallelism of two rotary shafts of the dual-shaft hinge.
2. Description of the Related Art
There are various pivotally openable/closable electronic apparatuses such as notebooks, mobile phones, PDA, digital image capturers and electronic books. The electronic apparatus has a display module (such as a screen) and an apparatus body module (such as a mainframe/keyboard). In general, one single rotary shaft is disposed between the display module and the apparatus body module, whereby the display module can be freely reciprocally rotated under external force. By means of the rotary shaft, the display module can be pivotally opened/closed to stretch or unstretch the electronic apparatus for operating or storing the electronic apparatus. In general, the pivotally opening angle of such single-shaft electronic apparatus is smaller than 180 degrees.
In order to operate the display module and the apparatus body module of the electronic apparatus in more operation modes and application ranges, a dual-shaft mechanism has been developed and arranged between the display module and the apparatus body module. The dual-shaft mechanism enables the display module and the apparatus body module to be relatively rotated by an angle within a range from zero degree to 360 degrees.
The dual-shaft mechanism is characterized in that two rotary shafts are disposed between the display module and the apparatus body module in parallel to each other. Each rotary shaft has a pivoted section at one end and a fixed section at the other end. The fixed sections of the rotary shafts are connected with the display module and the apparatus body module. The pivoted sections of the rotary shafts are together pivotally disposed on several bearing boards for supporting the rotary shafts and mounting the rotary shafts in a case. Accordingly, the display module and the apparatus body module can be respectively rotated by any angle around the bearing boards for operating the electronic apparatus in different modes.
However, the parallelism of the two rotary shafts is kept simply by means of the bearing boards. In general, the bearing board has the form of a plate so that the thickness of the periphery of the bearing board is generally quite limited. Therefore, the bearing boards can only respectively support the pivoted sections of the rotary shafts by the thickness of a plate. When operating the display module and/or the apparatus body module to force the two rotary shafts to rotate relative to each other, the fixed sections of the rotary shafts are driven by the rotational torque of the display module and the apparatus body module. Under such circumstance, the rotary shafts are likely to deflect to affect the parallelism of the two rotary shafts. After a long period of use, the rotary shafts are likely to swing, loosen or deflect. As a result, the electronic apparatus can be hardly stably operated.
In order to solve the above problem of unstable parallelism, it is necessary to increase the precision of the structures of the rotary shafts and the bearing boards and assemble these components at higher precision so as to lower the deflection of the rotary shafts. This will increase the difficulty in processing and increase the manufacturing cost.